1. Field of the Invention
The invention relates to a method of forming a contact opening, and more particularly, to a method of forming a contact opening through an uneven glasseous layer by using a sacrificial spin-on-glass layer in the manufacture of integrated circuits.
2. Description of the Prior Art
Referring to FIG. 1, there is shown a portion of a partially completed integrated circuit in which there is a silicon substrate 10. Semiconductor device regions 12 and 14 formed in and on the silicon substrate result in a uneven topography of the top surface of the substrate. A layer 16 of a glasseous material is deposited over the surface of the substrate. A layer of photoresist 20 coats the surface of the glasseous layer 16 and planarizes the substrate. The differing photoresist depths A and B will make it difficult for the photolithographic process. The smaller the geometry becomes, the smaller the depth of focus becomes. Thus, the greater the difference between A and B, the more difficult it is to resolve both A and B at the same time. The contact B would be unresolved.
U.S. Pat. Nos. 5,003,062 to Yen and 4,775,550 to Chu et al describe processes for planarization using spin-on-glass materials. These Patents are cited to show the general use of spin-on glass materials in the art.